Standard-sized magnetic record diskettes are commercially available which have a thin, flexible, circular magnetic record disc inside a rectangular envelope or jacket. Both the record disc and its jacket have a circular central opening for receiving a hub on the recording/playback machine which rotates the record disc during a recording or playback operation. The jacket has a rectangular notch in one edge which receives a finger in the recording/playback machine to enable the machine to record on the record disc in the jacket or to reproduce data previously recorded on the record disc. The jacket also has a small circular opening, located on one side of the larger central opening in the jacket and the disc, which is used for timing purposes in the operation of the recording/playback machine.
Diskettes of this general type are used to record on, and play back from, only one face of the record disc. The recording capacity of the opposite face of the disc is not used because the single rectangular notch and the single timing opening in the jacket cooperate with the recording/playback machine only for recording on or reproducing data from the one face of the record disc.